JAMES-3435 Fine grain LWT configuration for the Cassandra mailbox

[chibenwa]

| mailbox.read.strong.consistency
| Optional. Boolean, defaults to true. Disabling should be considered experimental.
If enabled, regular consistency level is used for read transactions for mailbox. Not doing so might result
in stale reads as the system.paxos table will not be checked for latest updates. Better performance are expected
by turning it off. Note that reads performed as part of write transactions are always performed with a strong
consistency.

| message.read.strong.consistency
| Optional. Boolean, defaults to true. Disabling should be considered experimental.
If enabled, regular consistency level is used for read transactions for message. Not doing so might result
in stale reads as the system.paxos table will not be checked for latest updates. Better performance are expected
by turning it off. Note that reads performed as part of write transactions are always performed with a strong
consistency.

| message.write.strong.consistency.unsafe
| Optional. Boolean, defaults to true. Disabling should be considered experimental and unsafe.
If enabled, Lightweight transactions will no longer be used upon messages operation (table `imapUidTable`).
As message flags updates relies so far on a read-before-write model, it exposes yourself to data races leading to
potentially update loss. Better performance are expected
by turning it off. Reads performed as part of write transaction are also performed with a relaxed consistency.

[chibenwa]

Build was 🍏 only squashed fixups.

[chibenwa]

If there's some reviewers out there that would like to give some <3 to this work?

[jeantil]

I gave it a cursory look but I haven't dug into mailbox code yet, so I have no idea what i'm looking at which is why I abstained to review further.